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Unit 8: Fundamental of Animations

file format notes
Conceptually, a GIF file describes a fixed-sized graphical area (the “logical screen”) populated
with zero or more “images”. Many GIF files have a single image that fills the entire logical
screen. Others divide the logical screen into separate sub-images. The images may also function
as animation frames in an animated GIF file, but again these need not fill the entire logical
screen.
The GIF has “.gif” file extension and these files start with a fixed-length header (“GIF87a” or
“GIF89a”) giving the version, followed by a fixed-length Logical Screen Descriptor giving the
size and other characteristics of the logical screen. The screen descriptor may also specify the
presence and size of a Global Colour Table, which follows next if present.
Thereafter, the file is divided into segments, each introduced by a 1-byte sentinel:
• An image (introduced by 0 × 2C, a comma ‘,’)

• An extension block (introduced by 0 × 21, an exclamation point ‘!’)
• The trailer (a single byte of value 0 × 3B, a semi-colon ‘;’), which should be the last byte of
the file.
An image starts with a fixed-length Image Descriptor, which may specify the presence and size
of a Local Colour Table (which follows next if present). The image data follow: one byte giving
the bit width of the unencoded symbols (which must be at least 2 bits wide, even for bi-colour
images), followed by a linked list of sub-blocks containing the LZW-encoded data.
Extension blocks (blocks that “extend” the 87a definition via a mechanism already defined in the
87a spec) consist of the sentinel, an additional byte specifying the type of extension, and a linked
list of sub-blocks with the extension data. Extension blocks that modify an image (like the Graphic
Control Extension that specifies the optional animation delay time and optional transparent
background colour) must immediately precede the segment with the image they refer to.

The linked lists used by the image data and the extension blocks consist of series of sub-blocks,
each sub-block beginning with a byte giving the number of subsequent data bytes in the sub-block
(1–255), the series terminated by the empty sub-block (a 0 byte).
This structure allows the file to be parsed even if not all parts are understood. A GIF marked 87a
may contain extension blocks. The intent is that a decoder can read and display the file without
the features covered in extensions it does not understand.
8.4.3 autodesk Maya

Autodesk Maya commonly shortened to Maya, is 3D computer graphics software that runs on
Microsoft Windows, Mac OS and Linux, originally developed by Alias Systems Corporation
(formerly Alias Wavefront) and currently owned and developed by Autodesk, Inc. It is used
to create interactive 3D applications, including video games, animated film, TV series or visual
effects. The product is named after the Sanskrit word Maya, the Hindu concept of illusion.

Maya is an application used to generate 3D assets for use in film, television, game development
and architecture. The software was initially released for the IRIX operating system. However, this
support was discontinued in August 2006 after the release of version 6.5. Maya was available in
both “Complete” and “Unlimited” editions until August 2008, when it was turned into a single suite.
Users define a virtual workspace (scene) to implement and edit media of a particular project.
Scenes can be saved in a variety of formats, the default being .mb (Maya Binary). Maya exposes
node graph architecture. Scene elements are node-based, each node having its own attributes and
customization. As a result, the visual representation of a scene is based entirely on a network of
interconnecting nodes, depending on each other information. For the convenience of viewing

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